Effects of hydrogen anneals on oxygen deficient SrTiO3−x single crystals

Jalan, Bharat; Engel‐Herbert, Roman; Mates, Thomas E.; Stemmer, Susanne

doi:10.1063/1.2969037

Cited by 46 publications

(46 citation statements)

References 25 publications

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“…In addition, some experiments give puzzling results that oxygen-deficient blue-black conducting SrTiO 3−δ transforms into a transparent insulating state upon annealing under an H 2 containing atmosphere. 18,19 These experimental results cannot be explained by the picture of hydrogen as a proton at interstitial sites (H + i ), suggesting that the role of hydrogen in SrTiO 3 should be reconsidered. In this Letter, interactions between hydrogen and oxygen vacancy are studied by first-principles calculations.…”

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confidence: 66%

Diversity of hydrogen configuration and its roles in SrTiO3−δ

2014

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As a source of carrier electron, various configurations of hydrogen in SrTiO3 are searched by using first-principles calculations. The most stable form of hydrogen is found to be H−, where doubly charged oxygen vacancy $V_{\rm O}^{2+}$VO2+ changes into singly charged ${\rm H}_{\rm O}^+$HO+. Most importantly, an additional H− is found to be weakly trapped by ${\rm H}_{\rm O}^+$HO+, which completely neutralizes carrier electrons by forming ${\rm (2H)}_{\rm O}^0$(2H)O0. These unexpected behaviors of hydrogen, which can explain reported experimental results, expand the role of the hydrogen in carrier-control technology in transition-metal oxides.

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confidence: 66%

Diversity of hydrogen configuration and its roles in SrTiO3−δ

2014

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“…The former route relies on the tunable m* of mobile electrons in STO, which is reported to be an order of magnitude higher than that of conventional semiconductors 16 while the electrical conductivity can be varied by doping with substitutional elements 17 or by introducing oxygen vacancies (SrTiO 3 À d ). 18 While undoped STO is a wide band gap ($3.2 eV) insulator, 19 doping with appropriate elements (e.g., La or Nd for Sr and/or Nb or Ta for Ti) or oxygen vacancies make the material semiconducting or metallic. However, substitutional doping is found to enhance carrier concentration only at the expense of Seebeck coefficient.…”

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confidence: 99%

Effect of oxygen vacancy distribution on the thermoelectric properties of La-doped SrTiO3 epitaxial thin films

Kumar

Abutaha

Hedhili

et al. 2012

Journal of Applied Physics

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A detailed study of the role of oxygen vacancies in determining the effective mass and high temperature (300–1000 K) thermoelectric properties of La-doped epitaxial SrTiO3 thin films is presented. It is observed that at intermediate temperatures, a transition from degenerate to non-degenerate behavior is observed in the Seebeck coefficient, but not electrical conductivity, which is attributed to heterogeneous oxygen non-stoichiometry. Heikes formula is found to be invalid for the films with oxygen vacancies. By fitting the spectroscopic ellipsometry (SE) data, obtained in the range 300–2100 nm, using a Drude-Lorentz dispersion relation with two Lorentz oscillators, the electrical and optical properties of the films are extracted. Using the excellent agreement between the transport properties extracted from SE modeling and direct electrical measurements, we demonstrate that an increase in concentration of oxygen vacancies results in a simultaneous increase of both carrier concentration and electron effective mass, resulting in a higher power factor.

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“…[17][18][19] In contrast, annealing O-deficient SrTiO 3 (STO) in H 2 gas resulted in a decrease of conductivity. This has been possibly attributed to H substituting in O vacancy sites and acting as an acceptor, 20 as has been seen in SrTi 1-x Fe x O 3-x/2 . 21 In bulk BTO crystals, theoretical calculations show that H acts as either an electron donor (interstitial defect) or acceptor (substituted for O), depending on the site, 22 with experiment confirming the existence of BTO "oxyhidrides" containing up to 20% of O substituted by hydrogen.…”

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confidence: 98%

Surface-hydrogen-induced metallization and rumpling in thin BaTiO3 films

Fredrickson

Demkov

2016

Phys. Rev. B

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We study theoretically metallization and polarization enhancement effects of H adsorption at the TiO 2 -terminated (001) BaTiO 3 surface. The clean BaTiO 3 slab does not polarize, because the slab is too thin to support a ferroelectric state. We find that the metallization of the surface is a strong function of hydrogen coverage, and that the insulating surfaces do not support a rumpling or polarization in BTO films, whereas all metallic surfaces do so. The donated charge from the adsorbed H transforms the TiO 2 into a metallic capping layer, stabilizing the ferroelectric state.

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Effects of hydrogen anneals on oxygen deficient SrTiO3−x single crystals

Cited by 46 publications

References 25 publications

Diversity of hydrogen configuration and its roles in SrTiO3−δ

Diversity of hydrogen configuration and its roles in SrTiO3−δ

Effect of oxygen vacancy distribution on the thermoelectric properties of La-doped SrTiO3 epitaxial thin films

Surface-hydrogen-induced metallization and rumpling in thin BaTiO3 films

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